Mechanical modelling of the source of glacial earthquakes in polar regions

• Main Author: Bonnet, Pauline
• Other Authors: Institut de Physique du Globe de Paris (IPGP (UMR_7154)), Institut national des sciences de l'Univers (INSU - CNRS)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Université Paris Cité, Anne Mangeney, Olivier Castelnau
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: HAL CCSD 2021
• Subjects: Glaciers; Iceberg; Capsize; Mechanical modelling; Greenland; Icequakes; Retournement; Modélisation mécanique; Groenland; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; [SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology; Vêlage; glacier
• Online Access: https://theses.hal.science/tel-04046993; https://theses.hal.science/tel-04046993/document; https://theses.hal.science/tel-04046993/file/BONNET_Pauline_va.pdf

Estimating the mass balance of the polar ice caps is a current challenge to understand the rapid evolution of these ice masses under the effect of climate change. The calving of icebergs represents a significant part of the mass loss of Greenland's glaciers. Their capsize near the terminus destabilises the glaciers. Using a reference fluid dynamics model, we quantified and characterised the interaction between water and a capsizing iceberg, and validated and improved a simplified iceberg capsize model. Then we built and validated a finite element model that reproduces the response of a glacier to the contact force of a capsizing iceberg at the terminus and that includes several rheologies of the glacier/rock interface and a visco-elastic behaviour of the ice. Using this comprehensive model, we reproduced surface displacements and stresses at the base of the glacier and analysed the influence of the parameters on the glacier response. We first modelled a glacier with an idealised geometry. Then we modelled a real glacier, the Helheim glacier, and for this we adjusted the model parameters using results from a reference glacier flow model. A strong dependence of the amplitude of the surface displacements on the Young's modulus of the ice and the length of the floating tongue is observed, but also a signature of the viscosity and the friction law parameters on these displacements. The results obtained with the full model open interesting perspectives on the estimation of the parameters of the rheology, geometry and basal friction laws through comparison with field observations. L’estimation du bilan de masse des calottes polaires est un enjeu actuel pour appréhender l’évolution rapide de ces masses glaciaires sous l’effet du changement climatique. Le vêlage d’icebergs représente une part importante de la perte de masse des glaciers du Groenland. Leur retournement proche du terminus déstabilise les glaciers. A l'aide d'un modèle de référence de dynamique des fluides, nous avons quantifié et caractérisé ...